Phenanthrene forms the basis for production of 9,10-phenanthraquinone and 2,2′-diphenic acid. It can also be used to synthesize anthracene via the isomerisation product of sym-octahydrophenanthrene. Electrically conductive substances, e.g., for use in batteries and solar cells, can be produced by the electrochemical conversion of phenanthrene diazonium salts in a solvent containing a conductive salt and subsequent doping with various ions (like sodium, barium, hydrogen etc). Liquid crystalline 7-n-alkyl-9, 10-dihydrophenanthrene-2-carboxylic acid ester, used for optical-electronic applications, can be synthesized from 9,10-dihydrophenanthrene. By cross-linking with p-xylene glycol and 4-toluenesulphonic acid, poly-condensed thermosetting resins are obtained for composites or temperature-resistant, electrically insulating coatings. A polyamide-polimide resin can be produced by oxidation of phenanthrene to phenanthrene-9,10-quinone and 9,10-diol, condensation with formaldehyde, oxidation to the polycarboxylic acid, formation of the anhydride and finally reaction with an aromatic diamine. This resin is suitable for use in high temperature insulators, printed circuit boards, and laminates. Phenanthrene has been proposed as a plasticizer for plastics and molding compounds; phenanthrene and alkylphenantherenes have been suggested as stabilizers for mineral oil products.
Phenanthrene, at a concentration of 5%, is the second most important coal tar constituent in terms of quantity after naphthalene. During primary distillation of coal tar, it is concentrated in the anthracene oil fraction. After crystallization of the anthracene residues, the phenanthrene is recovered as a fraction from the filtrate of this crystallization, or from the top fraction of crude anthracene distillation, by re-distillation. Technically pure grades of phenanthrene are obtained by sulfuric acid refining and re-crystallization from methanol, or by repeated rectification of the phenanthrene fraction. The accompanying substances can be separated either by partial sulphonation, or by partial condensation with formaldehyde and hydrogen chloride. Detailed search on patent databases and other literature did not result in any relevant reference.